Heat Exchanger; Raw Water Pump - Westerbeke 7.6KW BTD 60Hz Operator's Manual

COOLING SYSTEM
RAW WATER COOLING CIRCUIT
The raw water flow is created by a positive displacement
impeller pUl1lp. This pump draws water directly from the
ocean, lake, or river from a thru-hull opening through a hose
to the water strainer. The raw water passes from the strainer
through the pump to the heat exchanger (through the heat
exchanger tubes) where it cools the engine's circulating fresh
water coolant. The raw water is then discharged into the
water-injected exhaust elbow, mixing with, and cooling the
exhaust gasses. This mixture of exhaust gas and raw water is
drivcn through the stern tube and overboard.
HEAT EXCHANGER
Cool raw water flows through the inner tubes of the heat
exchanger. As the engine coolant passes around these tubes,
the heat of the internal engine is conducted to the raw water
which is then pumped into the exhaust system and dis-
charged. The engine coolant (now cooled) flows back
through the engine and the circuit repeats itself.
NOTE: Operating in silty and/or tropical yvaters may require
that a heat exchanger cleaning be perjrmned nlOre (4ten then
evClY 1000 hours.
HEAT EXCHANGER
CLEAN OUT BOTH ENDS
ZINC ANODE
NEW
___ RAW WATER DRAIN
OUT DEBRIS
REPLACE CLEAN AND
REUSE
A zinc anode, or pencil, is located in the raw water cooling
circuit within the heat exchanger. The purpose of the zinc
anode is to sacrifice itself to electrolysis action taking place
in the raw water cooling circuit, thereby reducing the effects
of electrolysis on other components of the system. The
condition of the zinc anode should be checked monthly and
the anode cleaned or replaced as required. Spare anodes
should be carried on board.
NOTE:
Electrolysis is the result of each particular installation
and vessel location; not that of the engine.
NOTE:
The threads of the zinc anodes are pipe threads and do
not require sealant. Sealant should not be used as
it
may
insulate the zinc from the metal of the heat exchanger
housing preventing electrolysis action on the zinc.
RAW WATER PUMP
The raw water pump is a self-priming, rotary pump with a
non-ferrous housing and a Neoprene impeller. The impeller
has flexible blades which wipe against a curved cam plate
within the impeller housing, producing the pumping action.
On no account should
this
pump
be
run dry.
There should
always be a spare impeller and impeller cover gasket aboard
(an impeller kit). Raw water pump impeller failures occur
when lubricant (raw water) is not present during engine
operation. Such failures are not watTantable, and operators
are cautioned to make sure raw water flow is present at
start-up. The raw water pump should be inspected
periodically for broken or torn impeller blades. See
MAINTENANCE SCHEDULE.
NOTE:
Should a failure occur with the pwnps internal parts
(seals and bearings). it may be more cost efJicient to
purchase a new pump and rebuild the original pump as
a ,spare.
Changing the Raw Water Pump Impeller
Q2-se the raw)Vater
intak~
valye. Remove the pump cover
and, using an impeller puller, screw drivers, or pliers,
carefully pry the impeller out of the pump. Install the new
impeller and gasket. Move the blades to conform to the
curved cam plate and push the impeller into the pumps hous-
ing. When assembling, apply a thin coating of lubricant to
the impeller and gasket.
Qp~n tl1~J1!~
water intake valy<;..
A
CAUTION:
If any of the vanes have broken off the
impeller, they must be found to prevent blockage in the
cooling circuit. They often
can
be found in the heat
exchanger.
INSPECTION: CHECK THE BASE OF
EACH BLADE BY BENDING VIGOROUSLY.
REPLACE THE IMPELLER IF THERE ARE
ANY CRACKS.
LIGHTLY GREASE THE
PUMP CHAMBER, O-RING,
AND IMPELLER WITH
GLYCERIN.
INSPECT THE a-RING
AND IMPELLER. REPLACE
IF THEY SHOW SIGNS
OF WEAR.
RAW WATER PUMP
Engines & Generators
18